Summertide

It was just before Summertide, the time when the twin planets, Opal and Quake, would orbit closest to their sun, subjecting both -- but Quake in particular -- to vast tidal forces. And it was to be the most violent Summertide ever, due to the Grand Conjunction of the system's stars and planets, something that happened only every 350,000 years.Access to the unstable Quake was supposed to be prohibited, but some very insistent travelers were determined to make the trip. Professor Darya Lang, who had made a career studying artifacts left by the long-vanished aliens called the Builders, had a hunch that during this unusal Summertide she might find the Builders themselves. Louis Nenda and the Cecropian Atvar H'sial had their own interests in Quake, and would do anything to get there. And Councilor Julius Graves was hunting murderers -- if they were hiding on Quake, he needed no one's permission to search for them.Planetary Administrators Hans Rebka and Max Perry had no choice but to go to Quake themselves -- risking their lives to protect the others -- and to learn, just maybe, the secret of Summertide and the Builders . . . "A well-made puzzle story in the manner of Arthur C. Clarke's Rama books." -- The New York Times